It is known that composites or alloys of nanocrystalline structure can be prepared by intense mechanical grinding, by crystallization of an amorphous precursor material obtained by quenching, or by condensation in vapor phase. By way of examples of manufacture of alloys by intensive mechanical grinding, reference can be made to international laid-open patent application No. WO-A-96/23906 and to European laid-open patent application No. EP-A-671,357.
If the nanocrystalline alloys that are so-obtained by mechanical grinding have some advantages, they usually have a specific surface area lower than 1 m.sup.2 /g. Such makes them inefficient for some very specific application where a high specific surface area is required, as is, for example, the case to obtain good catalysis or electrocatalysis results.
It is also known that one may obtain materials with a high specific surface area by leaching conventional alloys containing, in their structure, a leachable chemical element. Thus, for example, it is known that leaching of a NiAl alloy permits to obtain Raney Ni of high specific surface area. However, for thermodynamic reasons, this technology is restricted to a very small number of compounds of very specific composition and structure.